1. Field of the Invention
The invention relates to a presser foot device of a sewing machine capable of moving a presser foot up and down by automatic operation.
2. Description of the Related Art
Conventional sewing machines equipped with a presser foot for pressing a work cloth onto a bed employ various manual operating levers for moving the presser foot up and down. For example, an ordinary presser foot device employed in pattern sewing machines, that include embroidering machines, has a presser foot vertically movably connected to a body frame by a presser bar, an operating lever for switching the presser foot between an ascent position and a descent position, and a spring member urging the presser foot in the descending direction. During sewing, the presser foot is reciprocated within a small stroke at the descent position in accordance with cloth feeding actions. The presser foot is switched to the ascent position by manually operating the operating lever, for example, for replacement of a cloth holding frame that holds a work cloth to be sewed, or for checking the sewing start position in the work cloth held by the cloth holding frame, or at the time of a thread breakage. To start or restart sewing, the presser foot is switched to the descent position by manually operating the operating lever. Beside such manual presser foot devices, an automatic presser foot device has been developed for commercial use, which automatically moves a presser foot up and down by driving an actuator, such as a rotary solenoid or the like, in accordance with switch operations performed on various switches, such as externally provided push button switches.
However, it is difficult or impossible to freely adjust the amount of motion of actuators, such as solenoids. Therefore, to determine the position to which the presser foot is to be shifted, particularly, the position at the time of ascent, a structure having a member, integrated with the presser foot, is caused to impact an arm or the like, whereby the presser foot is stopped at a desired ascent position. However, impact noises are produced when the presser foot is raised, thus giving rise to noise problems. This structure also suffers from the high cost of solenoid actuators.